Third generation (3G) mobile systems, such as, for instance, universal mobile telecommunication systems (UMTS) standardized within the third generation partnership project (3GPP) have been based on wideband code division multiple access (WCDMA) radio access technology. Today, 3G systems are being deployed on a broad scale all around the world. After enhancing this technology by introducing high-speed downlink packet access (HSDPA) and an enhanced uplink, also referred to as high-speed uplink packet access (HSUPA), the next major step in evolution of the UMTS standard has brought the combination of orthogonal frequency division multiplexing (OFDM) for the downlink and single carrier frequency division multiplexing access (SC-FDMA) for the uplink. This system has been named long term evolution (LTE) since it has been intended to cope with future technology evolutions.
The LTE system represents efficient packet based radio access and radio access networks that provide full IP-based functionalities with low latency and low cost. The detailed system requirements are given in 3GPP TR 25.913, “Requirements for evolved UTRA (E-UTRA) and evolved UTRAN (E-UTRAN),” v8.0.0, January 2009, (available at http://www.3gpp.org/ and incorporated herein by reference). The Downlink will support data modulation schemes QPSK, 16QAM, and 64QAM and the Uplink will support BPSK, QPSK, 8PSK and 16QAM.
LTE's network access is to be extremely flexible, using a number of defined channel bandwidths between 1.25 and 20 MHz, contrasted with UMTS terrestrial radio access (UTRA) fixed 5 MHz channels. Spectral efficiency is increased by up to four-fold compared with UTRA, and improvements in architecture and signaling reduce round-trip latency. Multiple Input/Multiple Output (MIMO) antenna technology should enable 10 times as many users per cell as 3GPP's original WCDMA radio access technology. To suit as many frequency band allocation arrangements as possible, both paired (frequency division duplex FDD) and unpaired (time division duplex TDD) band operation is supported. LTE can co-exist with earlier 3GPP radio technologies, even in adjacent channels, and calls can be handed over to and from all 3GPP's previous radio access technologies.
FIG. 1 illustrates structure of a component carrier in LTE Release 8. The downlink component carrier of the 3GPP LTE Release 8 is sub-divided in the time-frequency domain in so-called sub-frames 100, each of which is divided into two downlink slots, one of which is shown in FIG. 1 as 120 corresponding to a time period Tslot. The first downlink slot comprises a control channel region within the first OFDM symbol(s). Each sub-frame consists of a given number of OFDM symbols in the time domain, each OFDM symbol spanning over the entire bandwidth of the component carrier.
In particular, the smallest unit of resources that can be assigned by a scheduler is a resource block also called physical resource block (PRB). A PRB 130 is defined as NsymbDL consecutive OFDM symbols in the time domain and NscRB consecutive sub-carriers in the frequency domain. In practice, the downlink resources are assigned in resource block pairs. A resource block pair consists of two resource blocks. It spans NscRB consecutive sub-carriers in the frequency domain and the entire 2·NsymbDL modulation symbols of the sub-frame in the time domain. NsymbDL may be either 6 or 7 resulting in either 12 or 14 OFDM symbols in total. Consequently, a physical resource block 130 consists of NsymbDL×NscRB resource elements corresponding to one slot in the time domain and 180 kHz in the frequency domain (further details on the downlink resource grid can be found, for example, in 3GPP TS 36.211, “Evolved universal terrestrial radio access (E-UTRA); physical channels and modulations (Release 8)”, version 8.9.0, December 2009, Section 6.2, freely available at www.3gpp.org. which is incorporated herein by reference). While it can happen that some resource elements within a resource block or resource block pair are not used even though it has been scheduled, for simplicity of the used terminology still the whole resource block or resource block pair is assigned. Examples for resource elements that are actually not assigned by a scheduler include reference signals, broadcast signals, synchronization signals, and resource elements used for various control signal or channel transmissions, as also illustrated in FIG. 3.
The number of physical resource blocks NRBDL in downlink depends on the downlink transmission bandwidth configured in the cell and is at present defined in LTE as being from the interval of 6 to 110 (P)RBs. It is common practice in LTE to denote the bandwidth either in units of Hz (e.g. 10 MHz) or in units of resource blocks, for the downlink case the cell bandwidth can equivalently expressed as 10 MHz or NRBDL=50 RB.
Before a UE can access an LTE cell, it performs a cell search procedure. This procedure enables the UE to determine the time and frequency parameters which are necessary to demodulate the downlink and to transmit uplink signals with the correct timing.
The first phase of the cell search includes an initial synchronization. Accordingly, the UE detects an LTE cell and decodes all the information required for registering to the detected cell. The procedure makes use of two physical signals which are broadcast in the central 62 subcarriers of each cell, the primary and secondary synchronization signals (PSS and SSS, respectively). These signals enable time and frequency synchronization. Their successful detection provides a UE with the physical cell-ID, cyclic prefix length, and information as to whether FDD or TDD is employed. In particular, in LTE, when a terminal is switched on, it detects the primary synchronization signal which for FDD is transmitted in the last OFDM symbol of the first time slot of the first subframe (subframe 0) in a radio frame (for TDD the location is slightly different, but still well-determined). This enables the terminal to acquire the slot boundary independently of the chosen cyclic prefix selected for the cell. After the mobile terminal has found the 5 millisecond timing (slot boundaries), the secondary synchronization signal is looked for. Both the PSS and SSS are transmitted on 62 of the 72 reserved subcarriers around the DC carrier. In the next step, the UE shall detect a physical broadcast channel (PBCH) which, similarly to the PSS and SSS is mapped only to the central 72 subcarriers of a cell. The PBCH contains the Master Information Block (MIB) including information about the system resources. In LTE up to Release 10, MIB had a length of 24 bits (14 bits of which are currently used and 10 bits are spare). MIB includes the following parameters:                Downlink system bandwidth,        Physical HARQ Indicator Channel (PHICH) structure, and        8 most significant bits of the System Frame Number (SFN)        
After successful detection of the master information block (MIB) which includes a limited number of the most frequently transmitted parameters essential for initial access to the cell, the terminal activates the system bandwidth, meaning that it has to be able to receive and detect signals across the indicated downlink system bandwidth. After acquiring the downlink system bandwidth, the UE may proceed with receiving further required system information on the so-called System Information Blocks (SIB). In LTE Release 10, SIB Type 1 to SIB Type 13 are defined, carrying different information elements required for certain operations. For instance, in case of FDD the SIB Type 2 (SIB2) includes the UL carrier frequency and the UL bandwidth.
The various SIBs are transmitted on a Physical Downlink Shared Channel (PDSCH) and thus (cf. details to PDSCH and PDCCH below) the respective allocations are assigned by a Physical Downlink Control Channel (PDCCH). Before the terminal (UE) is able to correctly detect such (or any) PDCCH, it needs to know the downlink system bandwidth from the MIB.
The data are mapped onto physical resource blocks by means of pairs of virtual resource blocks. A pair of virtual resource blocks is mapped onto a pair of physical resource blocks. The following two types of virtual resource blocks are defined according to their mapping on the physical resource blocks in LTE downlink:                Localised Virtual Resource Block (LVRB)        Distributed Virtual Resource Block (DVRB)        
In the localised transmission mode using the localised VRBs, the eNB has full control which and how many resource blocks are used, and should use this control usually to pick resource blocks that result in a large spectral efficiency. In most mobile communication systems, this results in adjacent physical resource blocks or multiple clusters of adjacent physical resource blocks for the transmission to a single user equipment, because the radio channel is coherent in the frequency domain, implying that if one physical resource block offers a large spectral efficiency, then it is very likely that an adjacent physical resource block offers a similarly large spectral efficiency. In the distributed transmission mode using the distributed VRBs, the physical resource blocks carrying data for the same UE are distributed across the frequency band in order to hit at least some physical resource blocks that offer a sufficiently large spectral efficiency, thereby obtaining frequency diversity. It may be noted that data that is targeting multiple receivers at the same time is usually mapped in the distributed fashion, as the probability that all receivers provide a sufficiently large spectral efficiency on the same localized resource blocks generally decreases with an increasing number of receivers.
In 3GPP LTE Release 8 there is only one component carrier in uplink and downlink. Within one DL subframe, the first 1 to 4 OFDM symbols are used for downlink control channel and downlink signal transmission (LTE control region). Downlink control signaling is basically carried by the following three physical channels:                Physical control format indicator channel (PCFICH) for indicating the number of OFDM symbols used for control signaling in a sub-frame (the size of the control channel region). For NRBDL>10, the PCFICH carries the control format indicator (CFI), which indicates a length of either 1, 2, or 3 OFDM symbols, while for NRbDL≦10, the CFI indicates a length of either 2, 3, or 4 OFDM symbols.        Physical hybrid ARQ indicator channel (PHICH) for carrying the downlink ACK/NACK associated with uplink data transmission. The duration of PHICH, the number of OFDM symbols used for PHICH, is configured by higher layer. For normal PHICH, the duration is 1 OFDM symbol. For extended PHICH, the duration is 2 to 3 OFDM symbols. The duration of PHICH puts a lower limit on the size of the DL control region determined from the PCFICH value.        Cell-specific reference signals (CRS) are transmitted on one or several of antenna ports 0 to 3. In a normal subframe, CRS is distributed within the subframe across the whole bandwidth. In an MBSFN subframe, CRS shall only be transmitted in the non-MBSFN region, DL control region, of the MBSFN subframe.        Physical downlink control channel (PDCCH) for carrying downlink scheduling assignments and uplink scheduling assignments.        
The PCFICH is sent from a known position that depends on the downlink system bandwidth value within the control signaling region of a downlink sub-frame using a known pre-defined modulation and coding scheme. The user equipment decodes the PCFICH in order to obtain information about a size of the control signaling region in a sub-frame, for instance, the number of OFDM symbols. If the user equipment (UE) is unable to decode the PCFICH or if it obtains an erroneous PCFICH value, it will not be able to correctly decode the L1/L2 control signaling (PDCCH) comprised in the control signaling region, which may result in losing all resource assignments contained therein.
The PDCCH carries control information, such as, for instance, scheduling grants for allocating resources for downlink or uplink data transmission. A physical control channel is transmitted on an aggregation of one or several consecutive control channel elements (CCEs). Each CCE corresponds to a set of resource elements grouped to so-called resource element groups (REG). A control channel element typically corresponds to 9 resource element groups. A scheduling grant on PDCCH is defined based on control channel elements (CCE). Resource element groups are used for defining the mapping of control channels to resource elements. Each REG consists of four consecutive resource elements excluding reference signals within the same OFDM symbol. REGs exist in the first one to four OFDM symbols within one sub-frame. The PDCCH for the user equipment is transmitted within the OFDM symbols according to the CFI value that is usually indicated by PCFICH in the sub-frame.
Another logical unit used in mapping of data onto physical resources in 3GPP LTE Release 8 (and later releases) is a resource block group (RBG). A resource block group is a set of consecutive (in frequency) physical resource blocks. The concept of RBG provides a possibility of addressing particular RBGs for the purpose of indicating a position of resources allocated for a receiving node (e.g. UE), in order to minimize the overhead for such an indication, thereby decreasing the control overhead to data ratio for a transmission. The size of RBG is currently specified to be 1, 2, 3, or 4 resource blocks, depending on the system bandwidth, in particular, on NRBDL. Further details of RBG mapping for PDSCH in LTE Release 8 may be found in 3GPP TS 36.213 “Evolved Universal terrestrial Radio Access (E-UTRA); Physical layer procedures”, v8.8.0, September 2009, Section 7.1.6.1, freely available at www.3gpp.org and incorporated herein by reference.
The UE shall monitor a set of PDCCH candidates on the serving cell for control information in every non-DRX subframe, where monitoring implies attempting to decode each of the PDCCHs in the set according to all the monitored downlink control information (DCI) formats. A DCI represents the required L1/L2 control information, for which more information can be found in 3GPP TS 36.212, “Evolved Universal terrestrial Radio Access (E-UTRA); Multiplexing and Channel Coding”, ver. 8.8.0, December 2009, Section 5.3.3, freely available at www.3gpp.org and incorporated herein by reference. The set of PDCCH candidates to monitor are defined in terms of search spaces.
UE monitors two types of search space: UE specific search space and common search space. Both UE specific search space and common search space consist of a generally different number of candidates for different aggregation levels defined by aggregating generally different CCEs.
PDCCH for system information is transmitted in common search space, so that all the UEs can receive system information by monitoring common search space.
Physical downlink shared channel (PDSCH) is used to transport user data. PDSCH is mapped to the remaining OFDM symbols within one sub-frame after PDCCH (with the possible exception of a limited number of resource elements, as indicated previously). The PDSCH resources allocated for one UE are in the units of resource block for each sub-frame. In LTE, DL data region starts after the DL control region within one subframe. In DL data region, CRS, PDSCH and—if configured—corresponding UE-specific or demodulation reference signals (DM-RS) are transmitted.
FIG. 3 shows an exemplary mapping of PDCCH 331-333 and PDSCH 350 within a sub-frame. The first three (in this example) OFDM symbols form a control channel region 390 (PDCCH region) and are used for L1/L2 control signaling. The remaining eleven OFDM symbols form data channel region (PDSCH region, in FIG. 3 only first 4 are shown, belonging to the first slot) and are used for transport of physical layer data (which may be control information of higher layers or user data). Within a resource block pairs of all sub-frames, cell-specific reference signals, so-called common reference signals 340 (CRS), are transmitted on one or several antenna ports 0 to 3.
Moreover, the sub-frame also includes UE-specific reference signals, so-called demodulation reference signals 380 (DM-RS) used by the user equipment for demodulating the PDSCH. The DM-RS are only transmitted within the resource blocks in which the PDSCH is allocated for a certain user equipment. In order to support downlink multiple input/multiple output (MIMO) with DM-RS, up to eight DM-RS layers are defined meaning that at most, MIMO of eight layers is supported in LTE Release 10. FIG. 4 shows only the case of 4 simultaneous employed DM-RS layers.
In September 2009 the 3GPP Partners made a formal submission to the ITU proposing that LTE Release 10 & beyond (LTE-Advanced) be evaluated as a candidate for IMT-Advanced. The ITU has coined the term IMT Advanced to identify mobile systems whose capabilities go beyond those of IMT 2000. In order to meet this new challenge, 3GPPs Organizational Partners have agreed to widen 3GPP's scope to include systems beyond 3G. In 3GPP, further advancements for E-UTRA (LTE-Advanced) should be studied in accordance with: 3GPP operator requirements for the evolution of E-UTRA and the need to meet/exceed the IMT-Advanced capabilities. The expectancy is that Advanced E-UTRA should provide substantially higher performance compared to what is expected to be the IMT-Advanced requirements in ITU-R.
LTE-A Rel.10 work started from March 2010 and was already stable in June 2011. The major features included in LTE-A Rel.10 included Carrier Aggregation, enhanced DL MIMO, UL MIMO, relay and etc.
According to 3GPP TS 36.300 v.10.2.0, “Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description”, December 2010, Section 5.5, in Carrier Aggregation (CA), two or more Component Carriers (CCs) are aggregated in order to support wider transmission bandwidths up to a total of 100 MHz. A UE may simultaneously receive or transmit on one or multiple CCs depending on its capabilities. It is possible to configure a UE to aggregate a different number of CCs in the UL and the DL.                The number of DL CCs that can be configured depends on the DL aggregation capability of the UE;        The number of UL CCs that can be configured depends on the UL aggregation capability of the UE;        It is not possible to configure a UE with more UL CCs than DL CCs.        
When CA is configured, a UE only has one RRC connection with the network. At RRC connection reestablishment/handover, one serving cell provides the NAS mobility information and the security input. The serving cell is referred to as Primary Cell (PCell). In the downlink, the carrier corresponding to the PCell is Downlink Primary Component Carrier (DL PCC) while in the uplink it is Uplink Primary Component Carrier (UL PCC).
Another key feature of the LTE-A is providing relaying functionality by means of introducing relay nodes to the UTRAN architecture of 3GPP LTE-A. Relaying is considered for LTE-A as a tool for improving the coverage of high data rates, group mobility, temporary network deployment, the cell edge throughput and/or to provide coverage in new areas. A relay node is wirelessly connected to radio access network via a donor cell. Depending on the relaying strategy, a relay node may be part of the donor cell or, alternatively, may control the cells on its own. In case the relay node is a part of the donor cell, the relay node does not have a cell identity on its own, however, may still have a relay ID. In the case the relay node controls cells on its own, it controls one or several cells and a unique physical layer cell identity is provided in each of the cells controlled by the relay.
LTE-A Release 11 work started from September 2011. The major features of LTE-A Release 11 include LTE carrier aggregation enhancements, Further Enhanced Non CA-based ICIC (inter-cell interference coordination) for LTE, Coordinated Multi-Point Operation (COMP) for LTE—Downlink and etc. Besides, LTE-A Release 11 also includes studies on Coordinated Multi-Point operation (CoMP) for LTE, Enhanced Uplink Transmission for LTE, further Downlink MIMO enhancements for LTE-Advanced.
During the study on CA enhancement, CoMP and DL MIMO, current PDCCH defined in Releases 8-10 shows some disadvantages: Beamforming or spatial multiplexing is not possible, frequency scheduling gain with localized allocation is not possible, because of only distributed DCI transmission is supported and frequency ICIC (Inter-Cell Interference Coordination) is not possible, because of random REG allocation among cells. In order to improve the situation, an enhanced PDCCH (E-PDCCH) is worked on, which would avoid the above problems.
A possibility provided by the LTE in order to improve battery lifetime is the discontinuous transmission (DTX) and reception (DRX). In order to provide a reasonable battery consumption of the terminal (UE), LTE Rel-8/9 as well as Rel-10 provide a concept of discontinuous reception (DRX). Accordingly, the terminal does not have to regularly monitor the control channels but rather can switch off the transmission and the reception over long periods and needs to activate the transceiver only at predefined or required time instances.
The following terms (parameters) describe the way DRX works:                “on-duration”: duration in downlink subframes that the UE waits for after waking up from DRX to receive PDCCHs. If the UE successfully decodes a PDCCH, the UE stays awake and starts the inactivity timer;        “inactivity-timer”: duration in downlink subframes that the UE waits to successfully decode a PDCCH, from the last successful decoding of a PDCCH. When PDCCH is not successfully decoded without the inactivity period, the UE re-enters DRX. The UE shall restart the inactivity timer following a single successful decoding of a PDCCH for a first transmission only (not for retransmissions); and        “active-time”: total duration that the UE is awake. This includes the “on-duration” of the DRX cycle, the time UE is performing continuous reception while the inactivity timer has not expired and the time UE is performing continuous reception while waiting for a DL retransmission after one hybrid ARQ (HARQ) round trip time (RTT). Based on the above, the minimum Active Time (here also called “active-time”) is of length equal to on-duration, and the maximum is undefined (infinite);        
There is only one DRX cycle per UE. All aggregated component carriers follow this DRX pattern.
In order to allow for further battery saving optimization, activation and deactivation of component carriers is introduced. Accordingly, a DL CC could be in one of the following three states: non-configured, configured but deactivated or active. When a DL CC is configured but deactivated, the UE does not need to receive the corresponding PDCCH or PDSCH and is also not required to perform CQI measurements for that CC. Conversely, when a downlink CC is active, the UE shall receive PDSCH and PDCCH (if present, transmitted), and is expected to be able to perform CQI measurements. After the configuration of the component carriers, in order to have PDCCH and PDSCH reception on the DL component as described above, the DL CC needs to be transitioned from the configured but deactivated state to the active state.
In the uplink however, a UE is always required to be able to transmit on PUSCH on any configured uplink CC when scheduled on the corresponding PDCCH (there is no explicit activation of uplink CCs).
In the past releases, semi-persistent scheduling (SPS) was introduced in order to reduce control channel overheads for applications that require persistent radio resource allocation such as voice over IP. SPS therefore introduces a persistent allocation of the physical resource blocks which a user should decode on the downlink or which he can transmit on the uplink. Up to now, however, the SPS feature is not very widely used.
Without SPS, in the downlink and uplink, eNB dynamically allocates resources to UEs at each TTI via the L1/L2 (layer 1/layer 2) control channel(s) (PDCCH) where the UEs are addressed via their specific C-RNTIs. TTI is a transmission time interval which is a basic timing unit of the transmission. C-RNTI is a cell radio network temporal identity, which uniquely identifies a UE. The cyclical error check (CRC) of a PDCCH is masked with the addressed UE's C-RNTI. Only a UE with a matching C-RNTI can decode the PDCCH content correctly resulting in a positive CRC check. This kind of PDCCH signaling is also referred to as “dynamic grant”. A UE monitors at each TTI the L1/L2 control channel(s) for a dynamic grant in order to find a possible allocation (DL and UL) it is assigned to.
In addition, E-UTRAN can allocate uplink/downlink resources semi-persistently. When required, retransmissions are explicitly signaled via the L1/L2 control channel(s). Since retransmissions are scheduled, this kind of operation is referred to as semi-persistent scheduling (SPS). The benefit is that PDCCH resources for initial HARQ transmissions are saved. One example for a service, which might be scheduled by semi-persistent scheduling is voice over IP (VoIP). Every 20 ms a VoIP packets is generated by the speech codec during a talk-spurt. Therefore the eNB could allocate uplink or respectively downlink resources persistently every 20 ms, which could be then used for the transmission of the VoIP packets. In general, SPS is beneficial for services with a predictable traffic behavior, such as services with a constant bit rate, where the packet arrival time is periodic.
A UE also monitors the PDCCHs in subframe where it has been allocated resources persistently. A dynamic grant, PDCCH with a C-RNTI masked CRC, can override a semi-persistent allocation. In case the UE finds its C-RNTI on the L1/L2 control channel(s) in the sub-frames where the UE has a persistent resource(s) assigned, this L1/L2 control channel allocation overrides the persistent allocation for that TTI and the UE does follow the dynamic grant. When UE does not find a dynamic grant it will transmit and/or receive according to the persistent allocation.
The configuration of SPS is performed by RRC signaling. For example, the periodicity of the semi-persistent allocation is signaled within RRC. The activation of a semi-persistent allocation and also the exact timing as well as the physical resources and transport format parameters are sent via PDCCH signaling. Once SPS is activated, UE follows the semi-persistent allocation according to the activation PDCCH with the configured periodicity.
In order to distinguish a dynamic PDCCH from a PDCCH that activates SPS, also referred to as SPS activation PDCCH, a separate identity is introduced. Basically the CRC of an SPS activation PDCCH is masked with this additional identity which is referred to as SPS C-RNTI. The size of the SPS C-RNTI is 16 bits, which is the same as the normal C-RNTI. Furthermore, the SPS C-RNTI is also UE specific, each UE configured for SPS is allocated a unique SPS C-RNTI. In case UE detects an SPS activation PDCCH, it will store the PDCCH content and apply it every SPS interval, periodicity signaled via RRC. Retransmissions of an SPS allocation are also signaled using the SPS C-RNTI.
Similarly to the activation of SPS, eNB can also deactivate the semi-persistent scheduling. As for the activation, also the deactivation of SPS resource (also denoted SPS resource release), is signaled by using a PDCCH.
Another improvement of Release 11 has been agreed as a working item for standardization and relates to providing low cost machine type communication (MTC) terminals based on LTE. Moreover, LTE RAN enhancements for diverse data applications are under study. The machine type communication traffic profiles include sporadic data access for exchange of relatively small data amounts. Such a type of communication is particularly relevant for applications which require always-on connectivity, such as smart phones, sporadic access for the purpose of checking e-mails or social network updates. The aim of the working item is to identify and specify mechanisms at the radio access network level that enable enhancing the ability of the LTE to handle diverse traffic profiles. In particular, the aim is to reduce the costs and complexity of terminals in order to extend the battery life. The machine type communication traffic is in general delay insensitive data traffic in which the terminals and/or eNodeB can wait for some time until the data is delivered. Such traffic may be, for instance, the planned data traffic including regular updates such as measurements or other reports. The amount of data exchange is typically rather small and can be delivered in few subframes. For instance, such data may be SMS type messages for controlling or reporting by a machine.
It is suggested that the MTC terminals shall only operate in the 1.4 MHz band only and shall be only addressable by E-PDCCH since the PDCCH is incompatible for different bandwidths. Addressing by E-PDCCH means that the DCI is transmitted in the PDSCH region. E-PDCCH is an enhanced PDCCH channel under study for release 11, which should provide more efficient and robust transmission.
The current initial synchronization procedure works only for all possible downlink system bandwidth sizes if the UE is capable of processing all the possible downlink system bandwidths. Up to the PBCH detection and reception it would be sufficient for the UE to support only a 1.4 MHz cell since the mapping of PSS/SSS to the central 62 subcarriers and the mapping of PBCH to the central 72 subcarriers enables the detection of these signals and channel independent of the actual downlink bandwidth of the cell. However, this bandwidth is neither sufficient to complete the synchronization procedure (for instance, receiving the various SIB Type messages (on PDSCH)) nor to commence the regular operation in the cell (for instance, by completing the connection setup and starting monitoring the PDCCH and possibly receive data on PDSCH), nor to initiate a random access procedure.
In other words, at the latest after the detection of the PBCH, the UE needs to enable the full downlink system bandwidth processing chain, in a case without carrier aggregation up to 20 MHz (or 100-110 PRBs) need to be operable and within the capability of the UE hardware and software.
3GPP contribution R1-112669, “On support of low-cost MTC terminals with reduced Tx/Rx bandwidths”, August 2011, RAN1 meeting no. 66, freely available on www.3gpp.org suggests continuous (permanent) operation of the terminal at using a small operational bandwidth in a larger system bandwidth cell. In particular, it is proposed to define a UE with a narrower receiving (Rx)/transmitting (Tx) bandwidth than the eNodeB's Tx/Rx bandwidth. The following features are envisaged to support a 1.4 MHz capable MTC UE to access an eNodeB with a wider bandwidth:                Special PDCCHs are introduced and used for MTC UEs. The PDCCHs are transmitted within the central 1.4 MHz-wide part of DL carrier. E-PDCCH on PUSCH region may be used for MTC UEs.        System Information Block of the eNodeB for MTC UEs are separately transmitted from those for legacy UEs and within the central 1.4 MHz wide part. Paging signals for MTC UEs are also transmitted within the central part.        Some of the reserved bits in PBCH may be used for MTC UEs, or X-PBCH might be transmitted within the central 1.4 MHz-wide part.        As located on the both edges of UL carrier, legacy PUCCHs are not used for transmission of UCI from MTC UEs. Alternatively, PUSCH is used for the UCI transmission.        All PRACH slots are located in the central 1.4 MHz-wide part. Alternatively, different PRACH configurations are configured for legacy UEs and MTC UEs.        
As can be seen, each of these points is introducing a new functionality for the UE and requires the corresponding support at the eNodeB side as well. Furthermore, the eNodeB would be tasked to manage the collision-free operation of channels and signals between such proposed MTC UEs and “regular” UEs.
According to R1-112669, the PDCCH is transmitted within the central 1.4 MHz-wide part of the downlink carrier. E-PDCCH or PDSCH region may be used for MTC UEs. Shared channel is only transmitted within the central 1.4 MHz wide part of the downlink carrier. Thus, the eNodeB scheduling and link adaptation has to manage coexistence of different bandwidth capabilities. The frequency scheduling flexibility for an MTC PDSCH and PUSCH is extremely limited, since only central 1.4 MHz are available. This may cause congestion of the central bandwidth in the case of simultaneous access by multiple MTC UEs on the PDCCH as well as PDSCH. The relative control signaling overhead is also substantial, since large packets need to be segmented and transmitted and consequently indicated by control signaling in multiple subframes.
The main task of the present invention is to enable an operation of a low-power-consumption device that is capable of integrating into the existing radio access network without major modifications, particularly for existing start-up and device attachment/registration procedures, while still able to operate at low power consumption during times of little or no data activity. At the same time, the target is to simplify the eNodeB's job of handling and coordinating the resources and transmissions to and from “regular” UEs and low-cost UEs.